This feasibility study demonstrates that the boundary between porcine subcutaneous fat and longissimus muscle can be detected with a probe using optical fibers to illuminate and detect anatomical boundaries. A relatively large optical window (approximately 3 mm2) seemed to give the best resolution of fat to muscle boundaries, whereas a smaller window gave a better resolution of marbling. Scattered, obliquely sectioned optical fibers gave reflectance spectra of fat and muscle that were relatively flat and parallel (fat > muscle). Thus, white light may be used with optical fibers to detect fat to muscle boundaries, although the greatest monochromatic separation was at 820 nm. In comparing measurements made as the probe penetrated the meat with those made as the probe was withdrawn, structures appeared to be deeper on the way in than on the way out, because of compression of the meat. Multichannel operation allowed tissue transmittance to be measured as well as reflectance and channels to be averaged to improve performance. These observations will be useful in developing new apparatus to measure fat depth and meat quality in one operation using optical fibers.